This research proposal is concerned with the molecular mechanisms involved in the expression and control of drug resistance genes carried by the extrachromosomal element, R plasmid (R factor), present in drug resistant bacteria. It is now well established that the antibiotic resistance of a bacterium carrying R plasmid is due to a production of an R plasmid-coded enzyme which modifies and inactivates the target antibiotic. However, due to the lack of comprehensive studies on the transcription of R plasmid genes in general, no detailed information is available for the control of R plasmid gene expression. Our major objectives are: l. Comprehensive characterization of transcriptional processes and transcripts of R plasmid genes in vivo and in vitro. 2. In vitro synthesis of R plasmid-specific proteins directed by plasmid DNA or RNA transcripts from it. 3. Transcriptional control of R plasmid gene expression with a special attention to the catabolite repression of the plasmid genes at the transcriptional level. 4. Characterization of multi-copy R plasmid DNA in relation to DNA replication and transcription.